The measurement of instantaneous horsepower is important in many applications involving ship and aircraft propulsion. Torque meters are presently used in these applications wherein it remains for the operator to determine the shaft horsepower by utilizing torque and shaft speed information. Non-contacting torque meters have been devised which sense torque by deriving a pair of phase related A.C. signals in which the phase shift is indicative of the twist in the shaft and therefore the torque.
A number of these systems are described in my U.S. Pat. Nos. 3,548,649 "Torque Measurement System Utilizing Shaft Deflection and Phase Displacement Technique" issued Dec. 22, 1970, and 3,538,762 "Phase Displacement Torque Measuring System with Shaft Misalignment Compensation Technique", issued Nov. 10, 1970.
These techniques use as a basis for the measurement a reference assembly comprising a first toothed wheel which will be called the reference toothed wheel mounted on a sleeve which is, in turn, mounted to the shaft to be measured. A second torque responsive toothed wheel is mounted to the shaft spaced a known distance from the point at which the reference assembly is attached to the shaft thus, as the shaft twists due to torque, the reference toothed wheel and the torque responsive toothed wheel move rotationally with respect to each other which can be detected by a pair of sensors as a phase change and using appropriate circuitry displayed as torque. The referenced patents have further modifications to compensate for shaft and sensor misalignment and to increase accuracy, however, the basis of torque measurement is the same.
Speed sensing is presently an accomplished fact in propulsion systems for ships and aircraft and therefore a speed signal is readily available and can be processed into a horsepower measurement system. By multiplying torque times shaft rpm an indication of horsepower can be obtained.
Known methods of measurement use contacting methods, such as electrical or mechanical brakes and require considerable equipment and expense without the benefits of measurement under actual operation conditions. Thus, the horsepower is derived in actual use by noting certain operating conditions, such as fuel consumption, speed, etc., which does not take into account losses due to inefficiency as the prime mover becomes older.
It is therefore an object of this invention to provide an accurate measurement system for determining the instantaneous horsepower output of a prime mover under actual operating conditions while in use.
It is another object of this invention to provide an accurate system for the measurement of the instantaneous horsepower output of a prime mover by non-contacting means.
It is a further object of this invention to provide an accurate system for the measurement of instantaneous horsepower output of a prime mover which is compact and will fit into a small space.
Still another object of this invention is to provide an accurate system for the measurement of instantaneous horsepower output of a prime mover which uses rotating sensing means for measurement at low rpm.
Still a further object of this invention is to provide an accurate system for the measurement of instantaneous horsepower output by a prime mover which is adaptable to torque measurement systems that provide compensation for shaft and sensor misalignment.
Yet another object of this invention is to provide an accurate system for the measurement of instantaneous horsepower output of a prime mover which has direct readout at a remote station.
These and other objects of this invention will become clear upon a careful reading of the specification along with the drawings and appended claims.